The effect of integration time on fluctuation measurements: calibrating an optical trap in the presence of motion blur

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  • 18 July 2006
Abstract
Dynamical instrument limitations, such as finite detection bandwidth, do not simply add statistical errors to fluctuation measurements, but can create significant systematic biases that affect the measurement of steady-state properties. In this article, we quantify the effect of time-averaging on video-imaged fluctuations of a harmonically confined Brownian particle, and present a novel method for extracting the true spring constant and diffusion coefficient by varying either the camera shutter speed or the confinement strength. These results are confirmed both numerically with a Brownian dynamics simulation, and experimentally with a laser optical trap. We also describe practical requirements for properly calibrating an optical trap using the blur-corrected equipartition analysis and power spectrum methods.

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